1. Field of the Invention
The present invention relates, generally, to a circuit arrangement for producing an output voltage of opposite polarity to the operating voltage, and a circuit arrangement which operates at a particularly low current level.
It also relates, in particular, to a circuit arrangement which, in an electronic device supplied with a battery voltage (for example), in a mobile radio set (mobile telephone) or a portable computer (laptop), produces a negative voltage from a positive voltage.
2. Description of the Prior Art
Circuit arrangements of this type are generally known. They are used, for example, in mobile radio sets which are supplied with a battery voltage and have one or more MMIC (Monolithic Microwave Integrated Circuit) Chips (for example, an MMIC power amplifier) based on MESFET technology, to produce a negative gate bias voltage for the MESFET(s). In the case of a first circuit variant, using which a negative voltage can be produced in a battery-powered electronic device, an AC voltage is produced by means of an oscillator or multivibrator, and is subsequently rectified. In the case of mobile telephones, it is likewise possible to produce a negative voltage by rectifying a received radio-frequency signal which is applied to the input of an MMIC power amplifier.
However, both of these methods have disadvantages. For example, in the case of the option mentioned first, an additional AC signal is produced by the oscillator in the electronic device which can adversely affect the operating characteristics of the device. For example, adjacent components in the electronic device, such as microprocessors, can be influenced, and this can lead to malfunctions.
In the case of the second method mentioned, it is particularly disadvantageous that the MMIC power amplifier is not switched on until after the radio-frequency signal has been applied, and can be operated only at relatively high signal levels.